I had the same problem some time ago. The email invitations would sometimes load the right tokens, sometimes the wrong ones, and sometimes none at all.

What made the difference for me was using the field replacement tags without the word 'TOKEN' in them. So use {ATTRIBUTE_1} instead of {TOKEN:ATTRIBUTE_1}. Include 'TOKEN' only in the field replacement tags you build into the survey itself.
This solved the problem for me. You can find my thread on this problem here: www.limesurvey.org/en/forum/design-issue...butes-in-invitations